Most vehicles are equipped with a brake system for retarding or stopping movement of the vehicle in a controlled manner. A typical brake system for an automobile or light truck includes a disc brake assembly for each of the front wheels and either a drum brake assembly or a disc brake assembly for each of the rear wheels. The brake assemblies are typically actuated by hydraulic or pneumatic pressure generated when an operator of the vehicle depresses a brake pedal. Structures for actuating such drum brake assemblies and disc brake assemblies are well known in the art as illustrated in U.S. Pat. No. 5,810,122.
A typical disc brake assembly includes an anchor bracket or similar support member carrier that is secured to a fixed, non-rotatable component of the vehicle. A pair of brake pads are supported on the anchor bracket by a disc straddling caliper for sliding movement relative to the anchor bracket. The brake pads have respective friction surfaces that are located on opposite sides of a brake rotor. The rotor, in turn, is connected to and rotatable with the wheel of the vehicle. To effect braking action, the brake pads are moved inwardly toward one another so as to frictionally engage the opposed sides of the brake rotor. Such frictional engagement causes retarding or stopping of the rotational movement of the brake rotor and, therefore, the wheel of the vehicle in a controlled manner. In the disc brake assembly a caliper selectively moves the friction pads into frictional engagement with the brake rotor. The caliper assembly typically includes guide pins or other components to slidably support the caliper housing relative to the fixed anchor bracket. The caliper housing is generally C-shaped, having an inboard leg adjacent the inboard brake pad and an outboard leg adjacent the outboard brake pad. One or more hydraulically or pneumatically actuated brake pistons are provided in respective cylindrical recesses. Early caliper brakes employed pistons in both the inboard and outboard portions of the caliper to actuate inboard and outboard brake pads respectively. More recently, one or more pistons are located to one side of the disc, typically in the inboard leg of the caliper adjacent to the inboard brake pad. In these more recent arrangements, when the brake pedal is depressed, the piston and the inboard leg of the caliper are urged apart from one another so that the piston and inboard friction pad are urged axially outwardly, while the outboard leg of the caliper and outboard friction pad are urged inwardly. The piston is disposed adjacent to the inboard brake pad and, therefore, urges it outwardly toward the inner side of the rotor. Because the caliper is slidably mounted on the pins of the anchor bracket, the outboard leg of the caliper and outboard brake pad are urged inwardly toward the outer side of the rotor. As result, the brake pads frictionally engage the opposed sides of the rotor. With this arrangement, the inboard friction pad needs to engage the disc or a similar impediment before outboard friction pad can begin to move toward the disc. When the pressure applied by the piston is released, a resilient annular roll-back piston seal serves to retract the piston to an initial position. Additional brake pad retraction springs may also be employed, such brakes are often called “sliding-caliper brakes” and are well known in the prior art.
In order to reliably obtain the braking force from the disc brake system having the guide pin type guide, the guide pin is required to smoothly slide in the guide hole in the direction perpendicular to the disc. Lubrication for the pins would be desirable. It would also be desirable to have a more positive and reliable translation of the caliper along the pins. Further, it would be desirable to eliminate the need for brake pad retraction springs.